The present invention relates generally to the reconditioning of firearms and, in particular, to an apparatus and method for crowning the barrel of a firearm.
A firearm barrel is typically an elongated steel tube with or without machined spiral grooves, or rifling, in the bore of the barrel. The crowning process is performed on an outlet face of the firearm barrel and consists of machining the face of the barrel so that the face is square, chamfering the face to a predetermined angle, and deburring the face, or removing any sharp edges caused by the machining or chamfering. The facing, chamfering, and deburring processes are performed with the use of separate cutting tools. Care must be taken to not damage the rifling in the bore when operating the cutting tools.
The present invention concerns an apparatus and method for crowning the muzzle end of a barrel of a firearm. The apparatus includes a pilot stem having an expandable collet for securing the stem in the bore of the barrel to ensure that the rifling in the bore remains undamaged during the crowning process. Various types of cutting tools can be rotatably mounted on the pilot stem. The apparatus includes an antirotation means, such as a brush or a deformable body, that frictionally engages the wall of the bore to permit the collet to be expanded and contracted. The apparatus preferably employs the use of serrated cutter blades for crowning the barrel.
The apparatus according to the present invention comprises: an elongated rod-like pilot stem with upper and lower ends, the upper end having a wrench socket formed thereon, and a downwardly facing pilot shoulder formed intermediate the upper and lower ends; a pair of expanders slidably received on the lower end of the pilot stem, one of the expanders engaging the pilot shoulder; an expandable collet slidably received on the pilot stem and disposed between the expanders; a nut threadably attached to the lower end of the pilot stem; a deformable body attached to the nut whereby when the deformable body is inserted into a bore at a muzzle end of a firearm, the deformable body frictionally engages a wall of the bore to prevent rotation of the nut and permit rotation of the pilot stem relative to the nut in an engaging direction to expand the collet into contact with the wall of the bore; and a cutting tool rotatably received on the pilot stem at the upper end for engaging an end surface of the muzzle end.
The method according to the present invention comprises the steps of: a) inserting an expandable collet on a pilot stem attached to a deformable body a predetermined distance into a bore at a muzzle end of a firearm barrel and frictionally engaging a wall of the bore with the deformable body; b) rotating the pilot stem to expand the collet into engagement with the wall of the bore; c) mounting a cutting tool on an upper end of the pilot stem and rotating the cutting tool relative to the pilot stem against an end surface of the muzzle end; d) removing the cutting tool from the pilot stem; e) rotating the pilot stem to retract the collet out of engagement with the wall of the bore; and f) removing the pilot stem, the collet and the deformable body from the bore.